1. Field of the Invention
The present invention generally relates to a sample retrieval device for aerosol collection.
2. Discussion of the Related Art
Aerosol sampling has become an indispensable process used in a wide range of applications such as, for example, environmental studies, detection of airborne biological or chemical warfare agents, exploration of cosmos, etc. The collection of the impurities, especially in air, can be realized by filtering many particles out of the air. The detection of the collected particles can be performed by, among others, sophisticated diagnosing equipment, e.g., time-of-flight spectrometers.
Recently, aerosol sample retrieval for chemical analysis by mass spectrometry has developed into an alternative method to on-site monitoring by separating a collection device from an analytical instrumentation. As a consequence, the use of aerosol collecting devices has been diversified and expanded to areas previously considered to be hardly accessible.
Some of the known collecting devices operate as an impacting type device configured to force entrained particles along a path, which leads the particles to an impactor plate, where these particles are collected upon impact and later analyzed. One of the difficulties in using impactors can be explained by a high kinetic energy possessed by particles entrained in a gas stream. As a consequence, the entrained particles can bounce off the impactor plate and re-entrain the gas stream thereby causing erroneous results during a subsequent analysis. Another difficulty includes a non-uniform deposit over the entire impaction plate, which is ordinarily mounted stationary mounted relative to a particle guide. However, it is desirable that a deposit be substantially uniform, because it reduces particle re-entrainment.
To remedy these problems, a “virtual” impactor has been developed to separate particulates from a fluid stream with techniques other than direct impaction. Virtual impactors may operate on a number of different principles, but all avoid actual “impact” as a means to separate particulates from a fluid in which the particulates are entrained. Critically, virtual impactors invariably rely on differences in particulate mass to induce inertial separation.
Still, the problems associated with actual impactors continue to persist in virtual impactors known for particle “wall loss,” i.e., unintended deposition of particulates on various surfaces of virtual impactor structures, especially at curved or bent portions. As a consequence, the virtual impactors are characterized complicated configurations, time-consuming installation and cost inefficient maintenance.
Thus, many of the known types of the actual and virtual impactors are characterized by a rather expensive and delicate structure difficult to install and maintain.
It would therefore be desirable to provide a cost-efficient, maintenance-friendly and rugged aerosol collection device, which can be coupled to a vehicle to collect aerosol samples in inaccessible or hazardous environment in a reliable manner.